The sixth in the periodic table of elements is, at the same time, among the most important ones. With about 180 ppm, carbon is only 17th on the list of terrestrial elements ' frequency, situated even after barium or sulfur -for comparison, the second -most frequent element, silicon, is about 1300 times as abundant as carbon. Still the latter is essential for the assembly of all organic matter. It is predestined for this central role especially due to its mid position in the periodic system and its associated ability to form stable substances with more electropositive and more electronegative reaction partners. Yet in the present text the organic chemistry resulting from these various bonding possibilities will only be mentioned if it is employed to modify carbon materials or, to put it in other words, the element itself as a material will be in the focus.
Another feature that gave reason to write this book was the occurrence of various allotrope modifi cations with in parts completely opposite properties. For the time being, this renders carbon one of the most interesting topics in materials science and research. Be it fullerenes, nanotubes or nanocrystalline diamond phases -they all are subject to intensive investigation and promise a multitude of applications, for example, in electronics, medicine, and nanotechnology. Nevertheless, it is hardly possible to assess the development within the last two decades and to perceive its impact on the multitalented carbon ' s perspectives in chemistry, material science, and physics, without an understanding of its longknown modifi cations, mainly graphite and diamond. Hence, the fi rst chapter summarizes the essential facts on the " classical " modifi cations and their properties, for only a solid comprehension of basic concepts and principles enables us to understand the properties of " new " carbon materials and to develop new ideas.
1.1 History
Elemental carbon in different shapes played a role in human life long before the term " element " was even coined. Charcoal and soot have been known and utilized for various purposes since ∼ 5000 BC . They were mainly obtained from wood and employed, for example, for metallurgic processes such as the production of iron.